Mine looks like this:
Ilmari Karonen, M.Sc.
Biomathematics Group, Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b), FI-00014 Univ. of Helsinki
Tel.: +358-41-456 3263, E-mail: <email@example.com>
That's basically all the relevant information, packed into the traditional 4 lines / 80 characters and preceded by the correct dash-dash-space-newline sequence. (Yes, I know that academic signatures often break that old rule these days, but I'm kind of a traditionalist about that. Besides, not having a foot-and-a-half-long e-mail signature is just plain common courtesy. The dashes help many e-mail readers recognize the signature and render it differently, and also omit it when quoting the message.)
I haven't actually included any mention of my position in the group, although there would be room to append "
doctoral student" or "
graduate student" after "
M.Sc." if I wanted to. It's not really as relevant as noting that my current highest degree is Master of Science, though, which already implies that I'm probably a grad student and not e.g. a postdoc or a faculty member. Anyone who wants to confirm that can just look me up on our group's website, anyway.
I also have a shorter signature, which just says:
Ilmari Karonen <firstname.lastname@example.org>
University of Helsinki, Dept. of Mathematics and Statistics
I use that mainly for informal correspondence with people I already know, who don't really need to be reminded of all the extra details in the full signature.